1. Field of the Invention
The present invention relates to a light source assembly, a backlight assembly having the light source assembly and a liquid crystal display apparatus having the light source assembly. More particularly, the present invention relates to a light source assembly that emits a heat generated in a light source unit, a backlight assembly having the light source assembly and a liquid crystal display apparatus having the light source assembly.
2. Description of the Related Art
Generally, liquid crystal has a physical property of interstate that is between solid state and liquid state. The arrangement of the liquid crystal is changed in accordance with the direction of electric field applied thereto, and then the light transmittance of the liquid crystal varies in accordance with the liquid crystal arrangement.
A liquid crystal display (LCD) apparatus displays an image containing information by adjusting the arrangement of the liquid crystal. The LCD apparatus is generally light and thin, and may be employed in various fields such as a notebook computer, a mobile telecommunication device or a liquid crystal television receiver, etc.
The LCD apparatus has a liquid crystal controlling part and a light supply part. The liquid crystal controlling part controls the arrangement of the liquid crystal, and the light supply part provides a light to the liquid crystal of the liquid crystal controlling part.
The liquid crystal controlling part generally includes a first substrate having a pixel electrode, a second substrate having a common electrode, and a liquid crystal layer interposed between the first and second substrates. The liquid crystal controlling part has a plurality of pixel electrodes in accordance with resolution of the liquid crystal display apparatus, and one common electrode corresponding the pixel electrodes. Each of the pixel electrodes is electrically connected to a thin film transistor, and a reference voltage is applied to the common electrode. The pixel electrode and the common electrode are generally transparent when the liquid crystal display apparatus has a light supply part.
The light supply part provides a light to the liquid crystal layer. The light passes through the pixel electrode, the liquid crystal layer and the common electrode. The quality of an image from the light controlling part depends on the brightness and brightness uniformity of the light supply part. As the brightness and the brightness uniformity of the light from the light supply part increase, the quality of the image is improved.
A conventional light supply part includes a cold cathode fluorescent lamp (CCFL) having a cylindrical shape. The CCFL has relatively high brightness and long lifetime. Further, the CCFL generates little heat compared to an incandescent lamp. Although the CCFL generates less heat than that of the incandescent lamp, the heat may induce problems.
Surface temperatures of the CCFL in the conventional liquid crystal display apparatus are shown in Table 1 below.
TABLE 1Surface Temperatures of the CCFL in Conventional LCD ApparatusLamp current (mA)4.04.55.05.56.06.45Lamp temperature (° C.)9093.597.6102106.9111.2Holder temperature (° C.)81.684.788.592.396.5100.2
In the conventional CCFL, light intensity increases in proportional to the lamp current. In addition, the surface temperatures of the holder and the lamp increase in proportional to the lamp current. In Table 1, when the CCFL has a lamp current of 6.45 mA, the lamp has a surface temperature of 111.2° C. and the holder has a surface temperature of 100.2° C.
Since the holder undergoes a deformation at a temperature greater than about 240° C., the holder may not be damaged by the lamp current of about 6.45 mA. However, an optical member that is in contact with the holder such as a light guide plate may be deformed or damaged at a temperature greater than about 100° C. Additionally, optical sheets disposed on the light guide plate may also be deformed or adhere to a light guide plate at a temperature greater than about 100° C.
The heat generated in the CCFL may deform optical members such as a light guide plate or an optical sheet. The heat also liquidizes the liquid crystal in the LCD panel, thereby deteriorating the displaying quality of the LCD apparatus.